The International Organization for Migration (IOM) says a record 432,761 refugees and migrants have crossed the Mediterranean Sea so far this year, more than doubling the total for all of 2014.

According to the figures released by the agency on September 11, an estimated 309,356 people had arrived by sea in Greece by earlier this week, with another 121,139 arriving in Italy, 2,166 in Spain, and 100 in Malta.

The influx has left Europe struggling to cope with the worst refugee crisis since World War II.

The UN refugee agency, UNHCR, earlier this week appealed to donors for $30.5 million to help it address the refugee crisis in Europe through 2016.

German authorities say around 450,000 refugees have arrived in Germany so far this year, including 37,000 in the first eight days of September alone.

Defense Minister Ursula von der Leyen said Germany has placed 4,000 troops on standby for this weekend alone to help with incoming refugees.

The European Union plans to distribute 160,000 refugees around the continent through mandatory quotas, strongly opposed by several member states.